1. Field of the Invention
This invention relates to a process for producing a non-woven fabric of cross-laminated warp web and weft webs. More particularly it relates to a process for producing the same wherein the weft webs are first prepared by ejecting a polymer in molten state, having a lower melting point than running elongated stocks described below and having a good affinity thereto, through orifices provided on the peripheral surface of a rotating vessel in the lateral direction of the vessel and toward elongated stocks arranged in parallel and in cylindrical form and running around the vessel vertically in the ejection direction of the polymer; causing the ejected polymer to form adhesive filaments adhered onto the elongated stocks to thereby fix the arrangement of the stocks; cutting open the resulting web and cutting the cut-open web by a length corresponding to a width of the above cross-laminated product; successively placing the cut webs onto the above warp web without gaps; and melting the adhesive filaments constituting the weft webs by heating the laminate to thereby bond the cross-points of the weft webs and the warp web to obtain the above cross-laminated product of precise lattice arrangement.
2. Description of the Prior Art
A process for producing non-woven fabrics comprising randomly arranged fibers, for example, mats or packs, according to a process for producing centrifugal candy-fluff-like fibers i.e. a process of centrifugally ejecting a polymer liquid from a number of small holes on the outer peripheral surface of a vessel rotating at a high velocity, solidifying the ejected material into random fibers and collecting these fibers to obtain a mat, has so far been disclosed (Japanese patent publication No. 6784/1974--Matsuda et al).
U.S. Pat. No. 3,357,807 to Stalego issued Dec. 12, 1967 discloses a process for producing mats, fibrous packs, etc. from glass fibers or other heat-softenable filaments ejected according to the above centrifugal process.
U.S. Pat. No. 3,723,218 to Gaffney, issued Mar. 27, 1973 discloses a process for producing a plastic net by intermittently preparing a doughnut-like material from a polymer liquid, dropping this material onto a rotating plate, and adhering it to a cylindrically and vertically arranged fibrous material prepared in advance, through a centrifugal force due to the rotation.
In any of the above prior art, the ejected glass or polymer forms a fibrous material from which a final product in the form of mats, packs or nets is obtained. In the present invention, however, the polymer to be ejected is an adhesive polymer, and the ejected polymer in the form of filament melts at the step of producing a lattice-form product comprising laminated warp and weft webs and loses the filament form, resulting in playing a role of fixing cross-points of the warp and weft webs together at the lamination step, and again playing an important role as an adhesive in the case where papers, films, fleece or the like are intended to be reinforced by the aimed lattice-form, laminated product.
Further, the greatest difficulty in the production of the lattice-form laminate resided in that when the weft webs was laminated on the warp web, the arrangement of the weft filaments (elongated stocks) forming the weft webs was notably disturbed; hence no orderly and regularly arranged lattice-form product has been obtained. It has become possible to obtain an orderly and regularly arranged lattice form product for the first time since it has become possible to fix the arrangement of the weft elongated stocks with the adhesive filaments according to the present invention. Furthermore, the adhesive polymer used in the present invention has a melting point lower than that of the elongated stocks in a cylindrical form, and in particular, a good affinity to the latter, and when the resulting web to constitute the above weft webs is wound into a roll of 5,000 to 6,000 m, it is necessary that the polymer has properties to cause no blocking. Thus, the ejected filaments in the present invention constitute adhesive polymer filaments fulfilling the above-mentioned conditions; hence such adhesive polymer filaments are not simple polymer filaments which directly constitute a product as seen in the above prior art.
As described above, the above various prior art and similar prior art have neither disclosed nor suggested such an inventive idea as in the present invention that by fixing the arrangement of elongated stocks by adhesive filaments, a success in producing the product of the present invention having a precisely arranged lattice-form structure has been brought about, and further such adhesive filaments melt by heating at the time of laminating the warp and weft webs to fix the cross-points of the warp and weft webs.